Ralph Waldo Emerson is credited with being the first to claim, "If a man can . . . make a better mousetrap . . . the world shall make a beaten path to his door." This touching faith that genius will prevail has inspired inventors and oddball tinkerers for a century. But these days shouting "Eureka" is not enough -- especially if you want to transform your idea into a new federal regulation.

Take the case of the single center, high-mounted brake light, an extremely inexpensive (estimates range from about $5 to $15) safety device that many at the National Highway Traffic Safety Administration (NHTSA) believe could cut rear-end auto collisions by 50 percent.

The gizmo is just an extra red brake light mounted in the center of the car just below the rear window. If you are following a car with this newfangled safety light, you see the braking signal sooner because it's smack in the middle of your field of vision, not down there with the bumper stickers.

According to two federally funded field studies, this safety add-on would eliminate half of all rear-end collisions. If that is true, the benefits would be staggering. In 1980, 4.2 million vehicles were hit from behind in the United States. These crashes killed 2,000 people, filled auto junkyards with tons of scrap metal and prompted thousands of accident victims to shout, "Whiplash."

Given the pitfalls of modern-day genius, of course there's a rub. The auto industry objected to a 1981 proposal to require this extra brake light on new cars, and, as a result, the proposed federal regulation is in limbo. But the flickering fate of this brake light is a reminder that Thomas Edison never had to grapple with the federal regulatory process.

Begin with the problem: The system of lights on the back of cars makes as much sense as a knee-high traffic light that uses red for stop and red for go. Rear lights are designed to tell you three things: the car is turning, the car is braking or, at night, there is a car ahead. But getting the message fast enough can be tricky since turn signals, brake lights and tail lights are generally red, invariably grouped together and always placed to the side, at eye level for a leprechaun.

Stimulated by federal dollars, researchers had identified these obvious problems by the early 1970s. But rear- end collisions are to auto safety what Latin America is to U.S. foreign policy: worth worrying about but never top priority. Researchers did run reaction time experiments on driving simulators or in contrived on-the-road tests, but failed to agree on a solution to the rear lighting problem.

Enter John Voevodsky, a Stanford PhD, Silicon Valley lone-wolf entrepreneur and sometime defense researcher. After witnessing a gruesome multicar pileup on a San Francisco freeway in the mid-1960s, Voevodsky took a month off from trying to discover the causes of war and tackled the problem of auto accidents instead. His solution was the Cyberlite, an amber lamp that pulses in harmony with the speed of braking. The greater the deceleration, the faster the Cyberlite flashes.

Voevodsky published his "general theory" of the Cyberlite in 1967, but nothing happened. "I went to all the auto companies, the auto suppliers, everybody. All I got was a big yawn," he recalls. Desperate to prove that his Cyberlite reduces accidents, Voevodsky applied to NHTSA for funding. He was rebuffed.

"Inventors are a rare breed of people," Voevodsky says now, "They'd sacrifice anything and anybody for their idea." Voevodsky put up his own money to field test the Cyberlite in 1972. He installed the device himself on 500 San Francisco taxis, using an equal number as a control group. Eleven months and 16 million cab-miles later, Voevodsky had his proof. Cabs with the Cyberlite were hit from behind 60 percent less often than the control group.

Robert Nicholson, an administrator in the research division at NHTSA, heard about Voevodsky's research, thought it was a "good study," but couldn't do much with it "because of budgetary constraints." In 1976 NHTSA finally had the research money to field test three of the most promising ideas in rear lighting. Nicholson was suspicious of the Cyberlite because of its complexity and cost (then $75, now $125): "We wondered whether you could get the same results with a single light without these gussied-up features."

An Alexandria consulting firm, the Essex Corporation, received a $182,000 contract for the year-long field test using 2,100 Washington taxicabs. In place of the Cyberlite, Nicholson used the single high-mounted brake light as one of the variables. Also tested against the control group were two other lighting systems: one with two high- mounted brake lights on each side; the other with separate brake and running lights.

After 60 million miles and 217 rear-end accidents, the results were startling. Only the single high-mounted brake light reduced accidents. The Essex report stated, "The single center high-mount group of taxicabs, sustained an accident rate 54 percent lower than the control group; and this difference was found to be statistically significant."

As Nicholson put it, "We were skeptical of the results, so we did it again." This time a $268,000 nationwide field test used AT&T's corporate fleet of 5,400 passenger cars. The second study in 1979 compared the single high-mounted brake light with a control group. The result? A 53 percent reduction in rear-end collisions.

Clear-cut and consistent experimental results like these are virtually unprecedented in safety research. The two field tests convinced Joan Claybrook, Ralph Nader's longtime sidekick who then headed NHTSA. On January 8, 1981, 12 days before the Carter administration left office, NHTSA published the proposed regulation in the Federal Register. It asked for comments on requiring this new brake light on all new cars beginning Sept. 1, 1983.

The auto industry, domestic and foreign, unleashed a firestorm of objections. Automakers contended that: the field tests didn't involve enough accidents and didn't include enough small cars; almost all the accidents were urban, and none involved serious injury; the new brake lights would cause confusing reflections on the rear windshield.

But the most revealing complaint came in the middle of a lengthy submission from General Motors. GM claimed that the new brake light "could result in . . . unacceptable appearance." Translated that meant: those brake lights are ugly.

Today, 21 months after the proposed regulation was published, NHTSA is still mulling the high-mounted brake light. A formal memo on what to do next (called a rule-making support paper) is wending its way through NHTSA.

The final decision rests with Ray Peck, the Reagan team's choice to head NHTSA. Peck complains that "the whole issue fell into the lap of the agency because of an unexpected result from a field study." But he insists, "This project has been going forward virtually at full speed. It's just a very complicated question."

Meanwhile, John Voevodsky is still selling his Cyberlite to motorcyclists from his Silicon Valley garage. And if today is like most days, there will be more than 10,000 rear-end collisions on American roads.